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Titolo:
ELECTROPHORETIC SEPARATION OF MYOSIN HEAVY-CHAIN ISOFORMS IN THE HUMAN M-VASTUS LATERALIS - REFERENCES TO REPRODUCIBILITY AND RELATIONSHIPSWITH FORCE, ELECTROMECHANICAL DELAY, FIBER CONDUCTION-VELOCITY, ENDURANCE AND ELECTROMYOGRAPHY
Autore:
TAYLOR AD; HUMPHRIES B; SMITH P; BRONKS R;
Indirizzi:
SO CROSS UNIV,BIOMECH LAB,POB 157 LISMORE NSW 2480 AUSTRALIA
Titolo Testata:
Archives of physiology and biochemistry
fascicolo: 1, volume: 105, anno: 1997,
pagine: 10 - 18
SICI:
1381-3455(1997)105:1<10:ESOMHI>2.0.ZU;2-#
Fonte:
ISI
Lingua:
ENG
Soggetto:
SINGLE MOTOR UNITS; SKELETAL-MUSCLE; CONTRACTIONS; FATIGUE; TENSION; EMG; PROTEINS; TWITCH; SLOW;
Keywords:
ELECTROCHEMICAL DELAY; ELECTROMYOGRAPHY; ELECTROPHORESIS; FORCE; ISOMETRIC ENDURANCE; MYOSIN HEAVY CHAIN;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
29
Recensione:
Indirizzi per estratti:
Citazione:
A.D. Taylor et al., "ELECTROPHORETIC SEPARATION OF MYOSIN HEAVY-CHAIN ISOFORMS IN THE HUMAN M-VASTUS LATERALIS - REFERENCES TO REPRODUCIBILITY AND RELATIONSHIPSWITH FORCE, ELECTROMECHANICAL DELAY, FIBER CONDUCTION-VELOCITY, ENDURANCE AND ELECTROMYOGRAPHY", Archives of physiology and biochemistry, 105(1), 1997, pp. 10-18

Abstract

The aim of this investigation was to determine the relationship between muscle performance and the myosin heavy chain (MNC) composition andthe reliability of electrophoretically determined MHC compositions. Atotal of thirty-one male subjects participated in the experiments. Maximal voluntary isometric contractions (MVC) of the knee extensors were performed at an arbitrary knee angle of 90 degrees and the followingvariables were recorded : maximal isometric force, muscle fibre conduction velocity (MFCV), electromechanical delay (EMD), maximal rate of force development (MRFD), median frequency of EMG (MF) and iEMG. Static isometric contractions of the knee extensors were held at an angle of 90 degrees using contractile forces of 10%, 50% and 100% MVC, respectively. These tests were conducted on separate days. Muscle biopsy samples were obtained from the left m. vastus lateralis before MVC and static endurance tests. MHC protein isoform differences,cere determined through sodium dodecyl-polyacrylamide gel electrophoresis (SDS-PAGE) followed by densitometric analysis. Type I-MHC compositions of the m. vastus lateralis ranged from 20-68% with a mean of 49 +/- 18%, mean type IIa-MHC and type IIb-MHC percentages were 35 +/- 16% and 16 +/- 10%,respectively. MHC compositions of duplicate biopsy samples were not significantly different from that of original samples. The coefficientsof variation calculated for duplicate biopsy samples suggested reasonable reproducibility for MHC isoform differentiation for the I-MHC andtype-II MHC composition (CV=12.6%). Differentiation between type IIa-MHC and the IIb-MHC was not always clear using the densitometric traces, Subjects with higher percentages of type II-MHC displayed significantly faster MFCV (r=0.67, P<0.1), isometric force development (r=0.68,P<0.1) and shorter periods of EMD (r=-0.72, P<0.05). There was also atendency toward faster MRFD in these subjects although results did nor reach significance. Endurance times for isometric contractions held at 10% 50% and 100% MVC to exhaustion were not correlated with MHC composition. No relationships between II-MHC composition and MF or iEMG were observed. It was suggested that surface electromyographic recordings obtained during isometric MVC did not reflect underlying differences in muscle fibre composition.

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Documento generato il 11/08/20 alle ore 12:19:10